Numerous sports and other fitness activities require that the participant keep track of a number of laps that are completed. For example, a jogger training on a track may run several laps during a training session. Often times, the person loses track of the number of laps completed and is thus unable to determine how far he has run, swam, biked, etc.
A known method for keeping track of the number of laps performed requires that the user manually activate a button or switch on a watch or the like each time a lap is completed. However, many times the runner forgets to activate the switch due, for example, to the monotony of the training.
There is therefore needed a lap counting device which can automatically counts laps without requiring any manual input from the user.
U.S. Pat. No. 4,530,105 describes an automatic lap counter which depends upon the change in the magnetic line of force of the north/south magnetic field for determining laps. The device operates using either an electronic or mechanical flux change detector to detect each 180.degree. shift and direction. Each 180.degree. change produces a pulse which is counted and displayed on a watch. The flux detector makes use of a compass needle mounted to, and operating, a cam plate. A cam follower switch contact is operated when the cam turns through 180.degree. responsive to the change and direction of the user. The cam follower closes a switch which activates a battery to produce the pulse. This known mechanical circuit is disadvantageous as only 180.degree. direction changes are detected. Further, the device requires that the user begin his training in a north or south direction in order to keep an accurate track of the laps. However, this is not necessarily convenient to the user as it often times does not provide the optimal starting point for the training. Still further, this known circuit is mechanically crude and can be subject to numerous erroneous lap counts due to the inaccuracy and fluctuation of the compass needle.
U.S. Pat. Nos. 4,991,126 and 4,482,255 disclose the use of Hall-effect elements for determining the direction and sense of the terrestial magnetic field. However, neither of these references provide any lap counting indications.
There is therefore needed a circuit which accurately and effectively resolves the earth's magnetic field in order to allow for a lap count determination without requiring any predetermined starting or stopping positions by the user.